1. Field of the Invention
This invention relates generally to methods and apparatus for heating biological specimens.
2. Prior Art
Medical analysis of human or animal tissue specimens comprises embedding the specimens in paraffin, cutting thin slices from the paraffin blocks, and placing the slices on microscope slides. The specimens are stained for improved viewing under a microscope. For further analysis, immunohistochemistry or similar techniques may be used, wherein monoclonal or polyclonal antibodies are used to identify tumors, infectious diseases, tissue constituents, etc. Some of the specimens may require the application of a heat retrieval method to permit the antibodies or probes access to the targeted antigen/epitope or sequence. The heat retrieval method comprises placing a retrieval solution on the slides, and heating the slides to between 80 and 120 degrees C. in a heating device such as a microwave, steamer, rice cooker, pressure cooker, or autoclave. Using a pressure cooker raises the boiling point of the solution and prevents it from boiling off at maximum cooker temperature, and also speeds up the process. After heating, the slides are removed from the heating device for immunohistochemistry analysis.
A major problem with heating slides in a conventional cooking device such as a microwave or pressure cooker is that the temperature and pressure cannot be monitored for precise and reliable results. According to laboratory governing bodies that issue operating standards for quality control, such as the College of American Pathologists (CAP), daily quality control measures should be implemented for such laboratory testing. Typical guidelines issued by a governing body are as follows:
1. Laboratory tests using a heating device should be have the temperature recorded.
2. Laboratory tests using pressure should have the pressure recorded.
3. The pH of solutions for heat retrieval procedures should be recorded at the temperature used.
4. Any electrical water bath should have a 3-prong power plug.
Conventional cooking devices cannot measure temperature, pressure, or pH. A tissue slide heating device which can measure pressure is sold under the trademark xe2x80x9cDECLOAKING CHAMBER DC2000xe2x80x9d by BioCare Medical of Walnut Creek, Calif. However, it does not measure temperature, so that it cannot be used for complying with laboratory quality control standards. Another problem is that it does not automatically adjust the total heating time to compensate for different amounts of materials in the cooker, since more massive contents must be heated longer than less contents.
The objectives of the present biological specimen heating device and quality control method are:
to heat biological specimens to a selectable temperature;
to heat the specimens under pressure;
to automatically adjust the total heating time to compensate for different amounts of materials;
to enable recording of the actual temperature inside the cooker for quality control;
to enable recording of the actual pressure inside the cooker for quality control;
to enable recording of the pH of the retrieval solutions at the set temperature for quality control;
to accurately indicate the pH of the retrieval solutions at the set temperature;
to provide redundancy in pH indication for reliability;
to provide redundancy in pressure indication for reliability; and
to increase safety.
Further objectives of the present invention will become apparent from a consideration of the drawings and ensuing description.
A heating device for heating biological specimens is comprised of an electric pressure cooker with a pressure gauge, and a temperature sensor connected to a controller with a temperature display and a temperature alert. The controller is arranged to heat the specimen at a selectable temperature for a selectable time period. The quality control process is comprised of placing in the cooker a heat sensitive pH indicating retrieval solution, and a heat and pressure sensitive steam strip. When the set temperature has been reached, the actual temperature and pressure are recorded. When the cooker is opened after heating, the pH indicating solution is checked for color change that indicates a pH change, and the steam strip is checked for color change that indicates predetermined temperature and pressure levels have been reached.